Radiation therapy in head and neck with telecobalt beam quality: Tolerance to 70 Gy dose in a five-week overall treatment time
Head and neck malignancies are associated with accelerated tumor repopulation when overall treatment time (OTT) extends beyond 28 days, potentially compromising the effectiveness of radiotherapy. To address this limitation, a treatment strategy was developed to reduce OTT by delivering a total radiation dose of 70 Gy over five weeks. In a pilot study involving high-grade head and neck malignancies, a total dose of 70 Gy was delivered using cobalt radiotherapy with tissue compensation at 2 Gy per fraction, administered either 7 fractions/week or 6 fractions/week. Good compliance with the full 70 Gy treatment course was observed. Radiation sequelae in the 7 fractions/week group included Grade III skin reactions in 16% of patients and Grade III mucositis in 26%, both considered acceptable. Based on these results, a randomized non-inferiority trial was conducted to compare acute toxicities between the 7 fractions/week and 5 fractions/week treatment arms, both delivering a total dose of 70 Gy. A total of 107 patients receiving concomitant chemoradiotherapy (CTRT) and 34 patients receiving neoadjuvant chemotherapy followed by concomitant chemoradiotherapy (NACT-CTRT) were treated with 70 Gy over five weeks. Another 99 CTRT patients and 42 NACT-CTRT patients received the same total dose of 70 Gy over seven weeks. In the 7 fractions/week arm, the observed Grade III–IV skin toxicity was 1.6%, and Grade III–IV mucosal toxicity was 12.7%, both significantly lower than the literature-reported value of 69% (p < 0.0001). For the 5 fractions/week arm, Grade III–IV skin toxicity was 3.2%, while Grade III–IV mucosal toxicity was <2.0%. Patient compliance was good in the 7 fractions/week study arm. As the tumor biologically effective dose increased by 19.4% (77.7 Gy [7 fractions/week] vs. 65.1 Gy [5 fractions/week]), improved local control is expected. Objective follow-up of this cohort is necessary to evaluate local control.
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